Pressure switch



Patented Aug. 7, 1945 PRESSURE SWITCH Carl V. Erickson, Kansas City,Kana, assignor to Air Communications, Inc., Kansas City, Mo., acorporation of Missouri Application May 8, 1944, Serial No. 534,569

9 Claims. (Cl. 200-83) This invention relates to a P s p r switch, andmore particularly to a switch of this character adapted for automaticoperation at pre-' determined atmospheric pressures for controllingcurrent volume of radio equipment; for example, the circuit volumerequired in operating aircraft radio equipment must be increased at highaltitudes and heretofore it has been necessary to operatemanually-controlled switches when such aircraft reach high altitudes.

The principal objects of the present invention are, therefore, toprovide for control of radio equipment responsive to predeterminedatmospheric pressures so as to increase the volume necessary foroperation at high altitudes; to provide a switch structure that issufficiently sensitive to changes in atmospheric pressures occurringwithin a differential of approximately five hundred feet; to provide aswitch structure with a diaphragm having a form to avoid fatigue andwhich is not affected by fatigue; to provide a switch structure capableof positive snap action at any predetermined altitude; and to provide aswitch of simple and economic construction and eiiicient in operation.

In accomplishing these and other objects of the present invention I haveprovided improved details of structure, the preferred form of which isillustrated in the accompanying drawing wherein: r

Fig. 1 is a perspective view of a pressure switch embodying the presentinvention.

Fig. 2 is a cross sectional view through the switch taken on the line2-2, Fig. 4, showing the diaphragm in normal position.

Fig. 3 is a similar cross sectional view through the switch showing thediaphragm in flexed position and in contact with the electrical circuit.

Fig. 4 is a plan view of the switch with parts I broken away to betterillustrate the invention.

Fig. 5 is a fragmentary perspective view of the diaphragm forming partof the present invention.

Referring more in detail to the drawing:

I designates a switch embodying my invention, having a housing 2, whichmay be of any suitable form although I have here shown it assubstantially square, and is preferably made of brass, bronze or thelike, although any suitable current conductive material may be used.Formed in the housing is a chamber 3 encompassed by an annular shoulder4, inset within a face of the housing and providing a seat for themarginal edge 5 of a diaphragm 6 secured on the annular shoulder 4 bysoldering or the like to completely close the chamber 3 and provide aspace I in the housing above said diaphragm. The diaphragm is preferablymade of electrical conducting material and shaped to provide aconcavo-convex central portion 8 to take a shape substantiallyconforming to an elastic curve, terminating in an outwardly flaredportion 9 merging through a radius it into an oppositely flaring portionit which carries the flat marginal edge 5. The portions 9 and I0, andthe curvature ll form an upwardly extending annular corrugation or ridgeI! on the diaphragm to render the outer portion relatively stifi so thatfiexure of the central portion 8 will not afiect the seal around theedge of the diaphragm. The diaphragm is preferably overstressed aroundthe base of the ridge l2 at l3 to aid in retaining the greatest possibleflexure in the central portion 8.

The formation of the ridge portion l2 on the diaphragm will form aboundary so that the manner of holding the outer edges does notinfluence in any large degree the performance of the diaphragm, but alsoallows in this formation the establishment of stresses in the diaphragmagainst which a pressure must be applied to the diaphragm to cause itssudden displacement. In general, the bulge of the diaphragm determinesthe difference between the values of pressure required for displacementand that required for return. The stresses in the outer ridge determinethe pressure which will be required for displacement. The stresses inthe ridge are controlled by the different bending radii and linearlengths of the arcs employed in its formation. It is well known thatafter release of the forming forces of the die in making the diaphragm,a slight return from the bend occurs which may be given as a small angleof return for each unit length of the arc. The application of such aprinciple will allow the production of proper stresses for definiteoperation of the diaphragm.

Mounted on the housing 2 and held in place by fastening devices, such asscrews It, in opposite comers of the housing, is a plate l5 preferablymade of insulating material and of a design to only partially cover theopening in said housing, thus leaving the diaphragm 6 exposed toatmospheric pressure. The plate I5 is provided with an aperture Hiadapted to receive an electric terminal I! of a length to extend aboveand slightly below the plate l5 as shown in Fig. 2. In the illustratedinstance, the aperture i6 is threaded and the terminalthreaded asindicated at i9, Fig. 2, to adapt it to be screwed into the aperture. Awasher 20 is Provided for the terminal which rests on the plate l5.Turned on the terminal i1 is a nut 2| adapted to lock the terminal inselected position.

The terminal is connected in circuit by a condoctor 22 fastenedthereon'with an ordinary nut 23. The outer end of the terminal I! isadapted to receive a tool for adjustment of the terminal relative to thediaphragm. In the present device I have shown a slot 2! in the end ofthe terminal adapted to receive a tool, such as a screw driver (notshown) for adjustment of the terminal in the plate.

The terminal ll may be threaded into the plate to adjust the distancebetween the end thereof and the diaphragm when in circuit-interruptingposition so that when contact is made, the screw will depress thecentral portion as indicated at 25, Fig. 3, and thereby reduce thedifferential pressure required to snap the diaphragm back incircuit-interrupting position. The return of the original positionoccurs with the release of the actuating fluid pressure through theactuating valve. The central portion is formed to take the shapesubstantially conforming to an elastic curve for the deflection of theflat plate rigidly held at the edges of the diaphragm, with a uniformpressure load.

The side of the housing 2 is provided, at substantially the level of themarginal edge of the diaphragm with a threaded recess 26 adapted toreceive a cap screw 21 for connecting a conductor 28 to said housing,forming a terminal for the oppodte side of the circuit.

The chamber I is preferably evacuated by suitable means (not shown)through aperture 29 in the side of the housing 2, having an enlargedthreaded recess ll therein, adapted to receive a set screw ll, wherebythe atmospheric pressure acting on the outside of the diaphragm forcesthe central portion 8 downwardly in the chamber 3. After the evacuationis completed the recess 30 is sealed with solder or other suitablematerial 32.

The switch may be mounted on the instrument panel of an airplane orother suitable place by ordinary means extending through apertures 33 inthe housing 2.

Operation of the device constructed and assembled as described is asfollows: After evacuation of the chamber the diaphragm will assume theconcave open position as shown in Fig. 2. As higher altitudes arereached, change in pressures will cause the diaphragm to flex outwardlyof the chamber and to assume an inverted curvature as shown in Fig. 3,and thus in its contacting position with the terminal I! whereby currentwill pass through the wire 22, terminal ll, diaphragm 8, housing 2 andconductor 28 to mmplete the circuit. In other words, evacuation of thechamber I permits the center of the diaphragm to be forced inwardlyunder external atmospheric premure at low altitudes. Reduction inatmospheric pressure causes the diaphragm to flex outwardly, and afterpassing the central point, the action is quite rapid to provide a snapaction which is effective in operating the switch.

At the p oper balance between the fluid pressure and stresses in thediaphragm, the diaphragm suddenly moves to a new flxed positionretaining this position until a reversal of pressure application hasoccurred, at which time the diaphragm reassumes its first position. Thissnap movement 01 the diaphragm is employed to definitely controlelectrical contacts.

A switch constructed in accordance with my invention is of light, simpleand inexpensive construction which may be mounted on the panel or backof the housing of an airplane in a suitable manner so that there may beno danger of loss of current through the mounting.

What I claim and desire to secure by Letters Patent is:

1. A snap action switch for opening and closing a control circuit to amechanism to be operated in response to change in atmospheric pressureincluding, a substantially rigid base member having a recess openingfrom a side thereof and provided with an inset shoulder encircling therecess, a snap action diaphragm having a rim portion sealed on theshoulder cooperating with the base member to form a closed chamber forcontaining an inert fluid medium under pressure less than atmosphericpressure, said snap action diaphragm being shaped to provide aconcaveconvex central portion therein, a terminal support bridging saidrecess, and an electrical terminal carried by the terminal support andhaving a contact portion coaxially of the diaphragm and adapted to beengaged thereby upon reversal of position 01' the central portion ofsaid diaphragm.

2. A snap action switch for opening and closing a control circuit to amechanism to be operated in response to change in atmospheric pressureincluding, a substantially rigid base member having a recess openingfrom a side thereof and provided with an inset shoulder encircling therecess, a snap action diaphragm having a rim portion sealed on theshoulder cooperating with the base member to form a closed chamber forcontaining an inert fluid medium under pressure less than atmosphericpressure, said snap action diaphragm being shaped to provide aconcave-convex central portion and having an annular ridge between saidcentral portion and said rim portion, a terminal support bridging saidrecess, and an electrical terminal carried by the terminal support andhaving a contact portion coaxially of the diaphragm and"adapted to beengaged thereby upon reversal of position of the central portion of saiddiaphragm.

3. A snap action switch for opening and closing a control circuit to amechanism to be operated in response to change in atmospheric pressureincluding, a substantially rigid base member having a recess openingfrom a side thereof and provided with an inset shoulder encircling therecess, a snap action diaphragm having a rim portion sealed on theshoulder cooperating with the base member to form a closed chamber forcontaining an inert fluid medium under pressure less than atmosphericpressure, said snap action diaphragm being shaped to provide aconcaveconvex central portion and having an annular ridge between saidcentral portion and said rim portion and an overstressed portion betweensaid ridge and said central portion to increase the snap action of saidcentral portion, a terminal support bridging said recess, and anelectrical tenninal carried by the terminal support and having a contactportion coaxially of the diaphragm and adapted to be engaged therebyupon reversal of position of the central portion of said dia hragm.

4. A snap action switch for opening and closing a control circuit to amechanism to be operated in response to change in atmospheric pressureincluding, a substantially rigid base member having a recess openingfrom a side thereof and provided with an inset shoulder encircling therecess, a snap action diaphragm having a rim portion sealed on theshoulder cooperating with the base member to form a closed chamber forcontaining an inert fluid medium under pressure less than atmosphericpressure, said snap action diaphragm being shaped to provide aconcaveconvex central portion and having an annular ridge between saidcentral portion and said rim portion and an overstressed portion betweensaid ridge and said central portion to increase the snap action of saidcentral portion, a terminal support bridging said recess, and anelectrical terminal carried by the terminal support and having a contactportion coaxially of the diaphragm and adapted to be engaged therebywhen the pressure in the closed chamber is greater than the atmosphericpressure.

5. A snap action switch for opening and closing a control circuit to amechanism to be operated in response to change in atmospheric pressureincluding, a substantially rigid base member having a recess openingfrom a side thereof and provided with an inset shoulder encircling therecess, a snap action diaphragm having a-rim portion sealed on theshoulder cooperating with the base member to form a closed chamber forcontaining an inert fluid medium under pressure less than atmospheric,pressure, said snap action diaphragm being shaped to provide aconcaveconvex central portion and having an annular ridge between saidcentral portion and said rim portion and an overstressed portion betweensaid ridge and said central portion to increase the snap action of saidcentral portion, a terminal support bridging said recess, an electricalterminal carried by the terminal support and having a contact portioncoaxially of the diaphragm and adapted to be engaged thereby when thepressure in the closed chamber is greater than the atmospheric pressure,and an electrical terminal attached to said base member.

6. A snap action switch for opening and closing a control circuit to amechanism to be operated in response to change in atmospheric pressureincluding, a substantially rigid base member having a recess openingfrom a side thereof and provided with an inset shoulder encircling therecess, a snap action diaphragm having a rim portion sealed on theshoulder cooperating with the base member to form a closed chamber forcontaining an inert fluid medium under pressure less than atmosphericpressure, said snap action diaphragm being shaped to provide a concaveconvex central portion and having an annular ridge between said centralportion and said rim portion and an overstressed portion between saidridge and said central portion to increase the snap action of saidcentral portion, a terminal convex portion to snap back and forth toopen and close said circuit.

'7. A device for controlling a mechanism in response to change inatmospheric pressure including, a base member having a recess openingfrom a side thereof and provided with an inset shoulder encircling therecess, a diaphragm having a rim portion sealed on said shouldercooperating with the base member to form a closed chamber for containingfluid medium under pressure less than atmospheric pressure, a terminalsupport bridging a part of said recess so that the side of saiddiaphragm opposite said chamber is open to atmosphere, and an electricalterminal carried by said support and having a contact portion coaxiallyof the diaphragm adapted to be engaged thereby when the atmosphericpressure on the outside of said diaphragm is less than the pres sure insaid closed chamber.

8. A device for controlling a mechanism in response to change inatmospheric pressure including, a base member having a recess openingfrom a side thereof and provided with an inset shoulder encircling therecess, a diaphragm having a rim portion sealed on said shouldercooperating with the base member to form a closed chamber for containingfluid medium, means for evacuating said chamber so that the fluid mediumtherein will be less than atmospheric pressure, a terminal supportbridging a part of said recess so that the side of said diaphragmopposite said chamber is open to atmosphere, and an electrical supportbridging said recess, and an electrical terminal carried by the terminalsupport and having a contact portion coaxially of the diaphragm wherebydiflerential in pressure on the outside of said diaphragm will cause theconcaveterminal carried by said support and having a contact portioncoaxially of the diaphragm adapted to be engaged thereby when theatmospheric pressure on the outside of said diaphragm is less than thepressure in said closed chamber.

9. A device for controlling a mechanism in response to change inatmospheric pressure including, a base member having a recess openingfrom a side thereof and provided with an inset shoulder encircling therecess, a diaphragm having a rim portion sealed on said shouldercooperating with the base member to form a closed chamber for containingfluid medium, means for evacuating said chamber so that the fluid mediumtherein will be less than atmospheric pressure, said diaphragm having aconcave-convex central portion, a terminal support bridging a part ofsaid recess so that the side of said diaphragm opposite said chamber isopen to atmosphere, and an electrical terminal carried by said supportand having a contact portion coaxially of the diaphragm adapted in beengaged by said concaveconvex central portion when the atmosphericpressure on the outside of said diaphragm is less than the pressure insaid closed chamber.

CARL V. ERICKBON.

